Stabilization process



Patented Dec. 26, 1950 STABILIZATION PROCESS William K. T. Glelm, Chicago, and Joseph A. Chenicek, Riverside, Ill., assignors to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware No Drawing. Application March'3, 1947,

Serial No. 732,142

13 Claims.

This invention relates to a stabilization process and more particularly to a method of preventing deterioration of unstable substances during storage or during treatment by incorporating therein a novel inhibitor.

Many substances are unstable in storage or during treatment and form undesirable gum, undergo discoloration, form sludges .or otherwise deteriorate due to oxidation, polymerization or other undesired reactions. This deteriorat on is particularly prevalent among organic compounds as, for example, motor fuel, especially cracked gasoline and polymer gasoline, etc., which contain unsaturated compounds and which tend to form gum or otherwise deteriorate during storage. Other hydrocarbon fractfons which tend to deteriorate in storage include, kerosene, lubricating oil and even higher boiling oils such as Diesel oil, gas oil and fuel oil which contain unsaturated and unstable compounds. Still other unsaturated compounds which tend to be unstable include acetylenes and particularly vinyl acetylene, butadiene, isoprene, styrene and other vinyl aromatics, acrylic acids, vinyl alcohol, vinyl acetate, vinyl pyridine, vinylldene chloride, fulvenes, aryl sulfonates and synthetic detergents, wetting agents, emulsifying agents, soap substitutes, etc., containing aryl sulfonates or other unstable compounds, rubber, plastics, fatty oi's, etc.

It is understood that the compoun s hereinbefore set forth are merely representative of organic compounds which may be treated in accordance with the present invention.

A class of compounds to which the present invention has particular applicability comprises edible fats and oils which generally are of animal or vegetable origin and which tend to become rancid, especially during long periods of storage prior to use. A suitable inhibitor must be one which will not impart bad odor and taste to either the edible oils and, fats or to the bakery goods in which they are us d, and must not be so volatile that they are removed during cooking or in deep fat frying. In addition, the inhibitor must be readily soluble in the oi s and fats and should carry over into the bakery goods and thereby serve to stabilize the baked products. Typical representatives of these oils include linseed oil, menhaden oil, cod liver oil, castor oil, olive oil, rapeseed oil, coconut oil, palm oil, corn oil, sesame oil, peanut oil, babassu oil, butter, fat, lard, beef tallow, etc., as well as hydrogenated oils and fats such as are sold under various trade names. It is understood that other oils and fats may be treated within the scope or the present in- 2 vention, including oils and fats which have previously been subjected to various treatments, such as blowing with air, heat treatment, etc.

Some inorganic compounds tends to deteriorate in storage and likewise may be treated by the novel method of the present invention. Examples of inorganic compounds which tend to deteriorate in storage or in use include cleansing compositions, particularly those containing peroxide salts which serve as an oxidizing or bleaching agent such as sodium perborate, sodium percarbonate, etc., which are unstable in the presence of an alkali, various alkali sulfur compounds such as sodium sulflte, etc.

Deterioration of unstable compounds or mixtures is prevented or at least retarded in accordance with the present invention by adding thereto a novel inhibitor as hereinafter set forth.

In a broad aspect the present invention relates to a stabilization process which comprises adding to an unstable substance an inhibitor comprising a bicyclic compound containing an aromatic ring joined to a heterocyclic oxygen ring, the aromatic ring being substituted by a hydroxy group in the position para to the bridge oxygen and by a hydrocarbon radical containing at least 3 carbon atoms in a position ortho to the hydroxy group.

In a more specific embodiment the present invention relates to a method of stabilizing organic compounds subject to oxidative deterioration which comprises adding thereto an inhibitor selected from the group consisting of para-hydroxy-coumarans and para-hydroxy-chromans having a hydrocarbon radical containing at least 3 carbon atoms substituted in a position ortho to the hydroxy group, in an amount suflicient to prevent or retard said deterioration.

In a still more specific embodiment the present invention relates to a method of stabilizing cracked gasoline which comprises incorporating therein 6-tertiary-alkyl-5-hydroxy-coumaran.

In still another specific embodiment the present invention relates to a method of stabilizing edible fats and oils against rancidity which comprises incorporating therein an inhibitor comprising a fi-alkyl-fi-hydroxy-coumaran, the alkyl radical containing at least 3 carbon atoms, in an amount sufllcient to retard rancidity development.

As hereinbefore set forth the novel inhibitor of the present invention comprises a bicyclic compound containing an aromatic ring joined to a heterocyclic oxygen ring, the aromatic ring being substituted by a hydroxy group in the position para to the bridge oxygen and by a hydrocarbon radical containing at least 3 carbon atoms in a position ortho to the hydroxy group. Particularly preferred. inhibitors comprise suitable substituted para-hydroxy-coumarans and para-hydroxy-chromans. It is understood, however, that other compounds falling within the broad classification hereinbefore set forth may be employed but not necessarily with equivalent results, such as similarly substituted 5-hydroxycoumarones, 6-hydroxy-chromens, etc.

methyl group ortho to the hydroxy radical,

While compounds falling within the classification hereinbefore set forth are active inhibitors. it has been found, after exten ive investigation, that certain types of compounds give better results in one class of materials to be stabilized. while other types of compounds give better results in other classes of materials to be stabilized. For example, it has been found that the 6-tertiary-alkyl-5-hydroxy-coumaransare of un xpectedly high potency for stabilizing gasoline while, on the ot er hand, 6-isopropyl and 6-secondary-butyl-5-hydroxy-coumarans appear to give unexceptionally high stability when used in lard. The particular inhibitor to. be used for best results in" any given instance will depend upon the susceptibility of the unstable material to be treated.

Once the coumaran or chroman is suitably substituted by a hydroxy group and by a hydrocarbon radical containing at least 3 carbon atoms in a position ortho thereto, the inhibitor may also contain other substituent groups. In fact, one of the best inhibitors contains two methyl groups attached in the 2-position as in 2,2-dimethyl-6-tertiary butyl 5 hydroxy coumaran It is understood that one or both of these methyl groups may be replaced by other radicals as hereinafter set forth. Thus, when one of the hydrogens in the 2-position of the hydroxy-chroman is substituted by an aryl radical, the resultant compound is a hydroxy flavan.

The chemical structure of the coumaran compounds, together with the numbering of the positions, is illustrated below.

The chemical tructure of the chroman compounds is iilust ted below.

hexyl, etc., and these substituents may them-- selves be substituted by hydroxy 01' amino groups.

The inhibitor is generally added to-the material to be treated in amounts of less than 1% by weight and preferably within the range of about 0.001% to about 0.1% by weight. The inhibitor may be used alone or it may be used in conjunction with inhibitor activators or synergists, dyes, antiknock agents, etc., depending upon the material to be treated. For example, when used in gasoline, lead tetraethyl, a dye and perhaps an inhibitor activator, such as particular types of alkylene polyamines, may be used. On the other hand, when used in edible fats and oils, a synergist, such as phosphoric acid, ascorbic acid, etc., will generally be used along with the inhibitor.

The inhibitors of the present invention may b prepared in any suitable manner, the preferred methods being illustrated in the following exam les.

The substituted hydroxy-coumarans of the present invention were prepared, in general, by reacting hydroquinone with methallyl chloride in the presence of a suitable salt of a strong base and a weak acid such as potas ium carbonate to form th corre pond n'z mono-m thall lether of hydroquinone. The mono-methallylet 'r of hydroquinone is t en r-arran-ed by means of heat to form 2-methaIlyl-hydroquinone, which is then refluxed in the presence of a suitabl acid. such as formic acid. to form 2,2- dimethyl-5 hydroxy-cournaran. The hydrocarbon substituent group is added in the 6-position by alkylating with an alcohol of the desired olefin in the presence of a suitable catalyst such as phosphoric acid. In place of methallyl chloride; methallyl bromide may be used and, in place of the alcohol for alkylation, the olefin or other olefin-producing substance may be employed. The following examples show the prepara i n of specific com ounds in d tail.

2,2-dimethyl 6 tertiary butyl 5 hydroxycoumaran was prepared as follows: 1 mol of hydroquinone, 1.2 mols methallyl chloride, 0.50 mol of potassium carbonate and 200 cc. of water were refluxed, while stirring for 48 hours working in a nitrogen atmosphere being optional. The water layer which was clear and colorless was drawn on and discarded. The hydroquinone methallyl ether-methallyl chloride mixture was dissolved in one liter of ethyl ether and the ether solution was washed, dried and evaporated. One hundred and forty grams of products were obtained and this amounts to a yield of 85% based on the hydroquinone. The product was heated slowly to 250 C. and, after cooling, was refluxed in an equal weight of 88% formic acid for 10 hours at 110 C., after which the formic acid was removed by atmospheric distillation. The hydroxy-coumaran was then reacted with tertiary-butyl alcohol in the presence of 85% phosphoric acid at .a temperature of '75-80 C. for one hour to form the desired 2,2 dimethyl-G-tertiary-butyl-5-hydroxy-coumaran. The final product was recovered after water washing, extraction with ether, water washing, drying, evaporation and recrystallization from alcohol or benzene.

2-methyl-5-hydroxy-coumaran was prepared by first forming the allyl ether of 4-methoxyphenol with allyl bromide in the presence of potassium carbonate and acetone. The compound was rearranged by means of heat to the 2-allylgnethoxyphenol which in turn was transformed invention but not with the intention of unduly 1 limiting the same.

EXAMPLE I A Mid-Continent thermally cracked gasoline was inhibited with 0.005% by weight of a standard wood tar inhibitor being marketed commercially, and the potency thereof, as indicated by the length of the induction period, was given an arbitrary inhibitor ratio of 1.0. Various substituted hydroxy-coumarans and hydroxy-chromans were tested in separate samples of the same thermally cracked gasoline, and the results are compared with the inhibitor ratio of 1.0 for the wood tar distillate, as shown in the following table.

Table I Inhibitor Inhibitor Ratio ouscnowuscnqqc It will be noted that the tertiary alkyl-substituted compounds were at least two times better than the hydroxy-coumaran which is unsubstituted in the 6-position. On the other hand, it is to be noted that the cyclohexyland benzyi-substituted compounds, while better than unsubstituted compounds, were not as effective as the tertiaryalkyl-substituted compounds when used in this particular gasoline. The tertiary-butyl-hydroxychroman is somewhat better than the unsubstituted hydroxy-chroman.

EXAMPLE II The inhibitors of the present invention, in amounts of 0.005% by weight, were utilized to stabilize lard which had a normal stability period of 1% hours as determined by the Swift" test. This test is described in detail in the article by A. E. King, H. L. Roschen and W. H. Irwin, which appeared in the Oil and Soap, vol. X, No. 6, pages 105 to 109 (1933). In general, this test comprises bubbling air through a sample of the lard until rancidity is determined organoleptically and by peroxide values. The results reported in the following table are the number of hours until the lard developed a peroxide number of 20.

6 It will be noted that the coumarans substituted in the 6-position approximately doubled the stability period of the particular lard tested.

EXAMPLE III A lard having a normal stability of 4 /2 hours was tested in a manner similar to that described in Example II. However, in these tests 0.02% by weight of inhibitor was used.

Table III Inhibitor ,esesssse It will be noted that all of the 6-alkyl substituted coumarans stabilized the lard for at least 40 hours as compared to only 28 hours for the coumaran unsubstituted in the 6-position. However, in this particular lard. the isopropyl and secondary-butyl-substituted compounds were better than the tertiary-substituted compounds, which are better in gasoline. This further illustrates the fact that the particular inhibitor to be used for best results must be selected on the basis of the particular unstable material to be treated.

We claim as our invention:

1. An olefinic gasoline containing a G-tertiaryaikyl-5-hydroxy-coumaran in an amount sumcient to retard oxidative deterioration of said gasoline.

2. A cracked gasoline containing from about 0.001% to about 0.1% by weight of 2-methyl-6- tertiary-butyl-5-hydroxy-coumaran,

3. Edible fats and oils containing as an inhibitor against rancidity a 2,2-dimethyl-6-isopropyl-5-hydroxy-coumaran.

4. Edible fats and oils containing as an inhibitor against rancidity a 2,2-dimethyl-6-secondary-butyl-5-hydroxy-coumaran.

5. An organic compound subject to oxidative deterioration containing, as an inhibitor for said oxidative deterioration, a 5-hydroxy-coumaran having an alkyl radical in the 6-position, said radical containing at least 3 carbon atoms.

6. Motor fuel subject to oxidative deterioration containing, as an inhibitor for said oxidative deterioration, a 6-tertiary-alkyl-S-hydroxy-coumaran.

'7. Cracked gasoline containing from about 0.001% to about 0.1% by weight of 2,2-dimethyl- 6-tertiary-butyl-5-hydroxy-coumaran.

8. Organic material normally subject to oxidative deterioration containing, as an inhibitor for said deterioration, a 5-hydroxy-coumaran substituted in the 6-position by a hydrocarbon group of at least 3 carbon atoms.

9. Olefinic gasoline containing, as an inhibitor against oxidative deterioration, a S-hydroXy-coumaran substituted in the 6-position by a hydrocarbon group of at least 3 carbon atoms.

10. Animal and vegetable fats and oils containing, as an inhibitor against rancidity, a 5- hydroxy-coumaran substituted in the 6-position by a hydrocarbon group of at least 3 carbon atoms.

11. Lard containing, as an inhibitor against rancidity, a 5-hydroxy-coumaran substituted in z the 6-position by a hydrocarbon group of at least 3 carbon atoms.

12. Lard containing, as an inhibitor against rancidity, a' B-hydroxy-coumaran substituted in the 8-position by an alkyl radical of at least 3 carbon atoms. v

18. Lard containing. as an inhibitor against rancidity, a. B-tertiary-alk'yl-fi-hydroxy-coumaran.

WILLIAM K. T. GLEIM. JOSEPH CHENICIK.

REFERENCES The following references are of record in the me of this patent:

UNITED STATES PATENTS 

7. CRACKED GASOLINE CONTAINING FROM ABOUT 0.001% TO ABOUT 0.1% BY WEIGHT OF 2,2-DIMETHYL6-TERTIARY-BUTYL-5-HYDROXY-COUMARAN. 